Section 4 Refrigeration plant, pipes, valves and fittings

4.1.1 New compressor types or developments of existing types are to be subjected to an agreed programme of type testing to complement the design appraisal and review of documentation.

4.1.2 Where it is proposed to treat the bearing surfaces either by local hardening or by chromium plating, then these processes are to be confined to the bearing area and not extended to the fillets. Particulars of the process are to be submitted.

4.1.3 Where ball or roller bearings are incorporated, they are to have a minimum life expectancy of 25 000 running hours, for the application in question.

4.1.4 A check valve is to be fitted to each compressor discharge.

4.1.5 Where off-loading devices are incorporated, arrangements are to be provided which indicate the extent of the off-loading being effected.

4.1.6 A pressure relief valve and/or safety disc is to be fitted between each compressor and its gas delivery stop valve in accordance with Pt 6, Ch 3, 4.15 Overpressure protection devices 4.15.5 and Pt 6, Ch 3, 4.15 Overpressure protection devices 4.15.6.

4.1.7 Stop valves are to be provided on compressor suctions and discharges.

4.1.8 Suction strainers and lubricating oil filters are to be provided and so arranged that they are easily accessible for cleaning or renewal of the filter elements, without substantial loss of refrigerant or lubricating oil.

4.1.9 The correct direction of rotation is to be permanently indicated.

4.1.10 Where any hermetic or semi-hermetic compressor has the electric motor cooled by the circulating refrigerant, the following arrangements are to be provided:

1. Refrigeration circuits are to contain no more than one hermetic or semi-hermetic compressor.

2. Every compressor motor is to be fitted with a thermal cut-out device to protect the motor against overheating.

3. In each refrigeration circuit containing a hermetic or semi-hermetic compressor, suitable arrangements shall be provided to remove debris and contaminants resulting from a motor failure. See Pt 6, Ch 3, 4.16 Filters, driers and moisture indicators 4.16.1.

4. The pressure envelope of any hermetic or semi-hermetic compressor exposed to the refrigerant pressure is to be designed and constructed in accordance with the requirements of Pt 5, Ch 11 and Ch 17 as applicable. Plans are to be submitted for consideration as required by Pt 5, Ch Pt 5, Ch 11, 1.6 Plans.

4.2.1 The specified minimum tensile strength of castings and forgings for crankshafts is to be selected within the following general limits:

1. Carbon and carbon-manganese steel castings -

   400 to 550 N/mm².

2. Carbon and carbon-manganese steel forgings (normalised and tempered) -

   400 to 600 N/mm².

3. Carbon and carbon-manganese steel forgings (quenched and tempered) -

   not exceeding 700 N/mm².

4. Alloy steel castings -

   not exceeding 700 N/mm².

5. Alloy steel forgings -

   not exceeding 1000 N/mm².

6. Spheroidal or nodular graphite iron castings -

   370 to 800 N/mm².

7. Grey iron castings -

   not less than 300 N/mm².

4.2.2 Where it is proposed to use materials outside the ranges specified in Pt 6, Ch 3, 4.2 Reciprocating compressors 4.2.1, details of the chemical composition, heat treatment and mechanical properties are to be submitted for approval.

4.2.3 Materials for components of reciprocating compressors such as crankshafts, pistons, piston rods, crank cases, etc. are to be produced at a works approved by LR and in general to be tested in accordance with the Rules for Materials.

4.2.4 A fully documented fatigue strength analysis is to be submitted indicating a factor of safety of 1,5 at the design loads based on a suitable fatigue strength criteria. Alternatively, the requirements of Pt 6, Ch 3, 4.2 Reciprocating compressors 4.2.5 to Pt 6, Ch 3, 4.2 Reciprocating compressors 4.2.9 may be used.

4.2.5 The diameter, d, of a compressor crankshaft using one of the refrigerants detailed in Pt 6, Ch 3, 2.5 Design pressures, is to be not less than that determined by the following formula, when all cranks are located between two main bearings:

where

a	=	distance between inner edge of one main bearing and the centreline of the crankpin nearest the centre of the span, in mm
b	=	distance from the centreline of the same crankpin to the inner edge of the adjacent main bearing, in mm
a + b	=	span between inner edges of main bearings, in mm
d p	=	proposed minimum diameter of crankshaft, in mm
p	=	design pressure, in MPa g, as defined in Pt 6, Ch 3, 2.5 Design pressures
D	=	diameter of cylinder, in mm
S	=	length of stroke, in mm
V c	=	1,0 for shafts having one cylinder per crank, or
	=	1,05 for 90° between adjacent cylinders on the same crankpin
	=	1,18 for 60° between adjacent cylinders on the same crankpin
	=	1,25 for 45° between adjacent cylinders on the same crankpin
	=	for the shaft and cylinder arrangements as detailed in Table 3.4.1 Angle between cylinders
Z	=	for steel
Z	=	for spheroidal or nodular graphite cast iron
Z	=	for grey cast iron
σu	=	specified minimum tensile strength of crankshaft material, in N/mm2.

4.2.6 Where the shaft is supported additionally by a centre bearing, the diameter is to be evaluated from the half shaft between the inner edges of the centre and outer main bearings. The diameter so found for the half shaft is to be increased by six per cent for the full length shaft diameter.

4.2.7 The dimensions of crankwebs are to be such that Bt ² is to be not less than given by the following formulae:

4.2.8 Fillets at the junction of crankwebs with crankpins or journals are to be machined to a radius not less than 0,05d. Smaller fillets, but of a radius not less than 0,025d, may be used provided the diameter of the crankpin or journal is not less than cd,

where

c	=	but to be taken as not less than 1,0
d	=	minimum diameter of crankshaft as required by Pt 6, Ch 3, 4.2 Reciprocating compressors 4.2.5, in mm
r	=	fillet radius, in mm.

4.2.9 Fillets and oil holes are to be rounded to an even contour and smooth finish.

4.2.10 An oil level sight glass is to be fitted to the crankcase.

4.2.11 Compressors with cylinder bores in excess of 50 mm diameter are to be provided with arrangements to relieve high cylinder pressures such as would result from `hydraulic lock' (i.e. liquid refrigerant in the cylinders). Alternatively the provision of positive means to prevent liquid refrigerant reaching the compressor may be accepted.

4.2.12 The crankcases of trunk piston compressors are to be designed to withstand a pressure equal to the maximum working pressure of the system. The crankcases of compressors of the crosshead type which are substantially isolated from the refrigerant circuit may be designed for lower pressures but are to be provided with relief valves adjusted to lift at a pressure not exceeding the design pressure, and discharging to a safe place.

4.2.13 A crankcase heater, arranged to be energised when the compressor is stopped, is to be provided.

4.3.1 For screw-type compressors, the materials of the rotors and casings are to be produced, and the manufacture is to be carried out, at a works approved by LR, and in general, they are to be tested in accordance with the Rules for general machinery forgings.

4.3.2 The rotor casing is to be designed for the maximum pressure to which it may be subjected, see Pt 6, Ch 3, 2.5 Design pressures.

4.3.3 Where gearing is fitted to increase the rotor speed and also to locate the rotors, the gearing is to comply with Pt 5, Ch 5 Gearing. The manufacturer's maximum allowable tolerances for clearances and backlash between mating rotors are to be stated.

4.4.1 The term `pressure vessel' will normally apply to receivers and heat exchangers, and does not include any of the following:

• Compressors.
• Liquid refrigerant pumps.
• Pipes and their fittings.

The use of plate heat exchangers will be specially considered on submission of plans, and special tests may be required.

4.4.2 Fusion welded steel pressure vessels exposed to the pressure of the refrigerants are to be constructed in accordance with the requirements of Pt 5, Ch 11 Other Pressure Vessels and Pt 5, Ch 17 Requirements for Fusion Welding of Pressure Vessels and Piping. Plans are to be submitted for consideration if required by Pt 5, Ch 11, 1.6 Plans.

4.4.3 Where ammonia is the refrigerant, the pressure vessels are to be constructed to at least Class 2/1 requirements.

4.4.4 Pressure vessels for the containment of primary refrigerants for use in conventional refrigeration circuits where the pressure/saturation temperature relationship applies are not required to be low temperature impact tested unless the design temperature is lower than minus 40°C.

4.4.5 Pressure vessels are to be thermally insulated to an extent which will minimise condensation of moisture from the surrounding atmosphere. The insulation is to be provided with an efficient vapour barrier and adequately protected from mechanical damage. Prior to applying the insulation, the steel surfaces are to be suitably protected against corrosion.

4.4.6 Each pressure vessel which may contain liquid refrigerant and which is capable of being isolated is to be protected with overpressure relief devices, see Pt 6, Ch 3, 4.15 Overpressure protection devices.

4.5.1 In order to minimise the risk of corrosion, where the refrigerant is ammonia, the material interface between the primary refrigerant and cooling water or secondary refrigerant is to be of a suitable grade of stainless steel. Carbon-manganese steel with a suitable inhibitor would also be acceptable.

4.5.2 Space is to be provided for the withdrawal and replacement of condenser and evaporator tubes, see Pt 6, Ch 3, 3.1 General 3.1.1.

4.5.3 Where ammonia is used as the refrigerant, the refrigerating plant is to comply with the following additional requirements:

1. Automatic air purgers are to be provided, with their discharges being led through water before venting to atmosphere.

2. The cooling water returns from sea-water cooled condensers are not to be led into the main machinery spaces.

3. Fresh water condenser cooling systems are to be provided with pH meters to activate audible and visual alarms in the event of an ammonia leak.

4.6.1 Primary refrigerating systems are to be provided with liquid receivers with sufficient capacity to hold the complete refrigerant charge to prevent emission of the refrigerant to the atmosphere during servicing or repairs.

4.6.2 Alternatively, in systems using a secondary refrigerant, with a number of units, smaller receivers may be used provided the system includes a common storage receiver with sufficient capacity to hold at least the primary refrigerant charge from two units. The common receiver is to be provided with the necessary crossover connections to facilitate transfer of refrigerant to and from each unit in the system.

4.7.1 Oil separators are to be provided at compressor discharges and are to be fitted with a control arrangement to enable the separated oil to be returned to the compressor crankcase. Wire gauze used in separators is to be sufficiently robust and well supported.

4.8.1 Refrigerated spaces may be cooled by air coolers or cooling grids on the ceiling, bulkheads, and sides. In order to minimise the dehydration of the cargo and the frosting of the air coolers or cooling grids, the installation is to be designed to maintain the required notation temperatures with a minimum of difference between the refrigerant and space temperatures.

4.8.2 Individual spaces are to have a minimum of two independent air coolers, each comprising one or more fans and one or more refrigerant circuits in a single casing and with isolating valves. Alternatively, multiple circuits each with their own fan(s), in a single cooler casing may each be regarded as a separate cooler, provided stop valves are fitted so that each circuit may be isolated.

4.8.3 For refrigerated spaces having a net volume of 300 m³ or less, a single cooler with one circuit will be accepted.

4.8.4 The refrigeration capacity of the air cooler arrangement is to be such that the notation temperature conditions can be maintained with any one independent cooler or circuit out of action. The capacities of the fans are also to be such that they can maintain the required air flow rates (see also Pt 6, Ch 3, 9.4 Air circulation and distribution) and uniform air temperature throughout the refrigerated spaces, when part or fully loaded with cargo, with any one cooler or fan out of action.

4.8.5 Air cooler fan motors are to be suitably enclosed to withstand the effects of moisture.

4.8.6 Means are to be provided for effectively defrosting air coolers. Air coolers are to be provided with trays of suitable depth arranged to collect all condensate. The trays are to be provided with drains at their lowest points to enable the condensate to be drained away when the refrigerated spaces are in service. Provision is to be made for the prevention of freezing of the condensate.

4.8.7 Air coolers are to be located such that when the refrigerated spaces are loaded with cargo, adequate space is provided for the inspection, servicing and renewal of controls, valves, fans and fan motors.

4.8.8 The cooling grids in each refrigerated space are to be arranged in not less than two sections, and each section is to be fitted with valves so that it can be shut off. The notation temperature conditions are to be capable of being maintained with any one section isolated. For spaces having a net volume of 300 m³ or less, a single section will be acceptable.

4.8.9 Steel air cooler circuits and cooling grids are to be suitably protected against external corrosion.

4.9.1 Pumped primary and/or secondary refrigerant systems are to have a minimum of two pumps. Each pump is to be capable of operating on all cargo chambers and maintaining full duty with any one pump out of operation.

4.9.2 Primary and, where appropriate, secondary refrigerant pumps are to be provided with pressure relief valves, see Pt 6, Ch 3, 4.15 Overpressure protection devices 4.15.13.

4.10.1 At least two separate condenser cooling water pumps are to be installed. One of the pumps may be considered as a standby pump and may be used for other purposes, provided that it is of adequate capacity and its use on other services does not interfere with the supply of cooling water to the condensers.

4.10.2 Not less than two sea inlets are to be provided supplying sea-water to the pumps for condenser cooling. It is recommended that one of the sea inlets be provided on the port side and the other on the starboard side. The sea inlets are to be fitted in accordance with Pt 5, Ch 13, 2.6 Piping systems − Installation.

4.10.3 The cooling water pumps and sea inlets are to be suitably valved and cross-connected with each condenser.

4.10.4 Suitable spring-loaded safety valves are to be provided in each cooling water circuit, see Pt 6, Ch 3, 4.15 Overpressure protection devices 4.15.13.

4.11.1 All piping, valves and fittings are to be suitable for the maximum pressure to which the system can be subjected and are to comply with the requirements of Pt 5, Ch 12 Piping Design Requirements.

4.11.2 Pipework for Ammonia (R–717) is to comply with Class 1 requirements.

4.11.3 In addition to visual examination of pipe welds, non-destructive examination of pipe welds is to be carried out in accordance with the requirements of Ch 13 Requirements for Welded Construction of the Rules for Materials, to the satisfaction of the Surveyors.

4.11.4 All steel pipework on the low temperature part of the system is to be protected against external corrosion. Protective coatings are to be removed from pipe surfaces to a distance of not less than 50 mm either side of the joint weld preparations prior to welding. On completion of welding and testing a protective coating is to be applied.

4.11.5 Where brine is the secondary refrigerant, piping and tanks should not be galvanised on the brine side. If any parts of the brine system have been galvanised, the brine cooling and return tanks are to be provided with a ventilating pipe or pipes led to the atmosphere in a location where no damage will arise from the gas discharged. The ventilation pipes are to be fitted with wire gauze diaphragms which can be readily renewed.

4.11.6 Copper piping is to be manufactured in accordance with Pt 5, Ch 12, 3 Copper and copper alloys except in the case of small air coolers having finned pipes of sizes not greater than 19 mm outside diameter, and which have been fabricated under workshop conditions. The finned pipes may have a minimum wall thickness of 0,5 mm when used with R–22 and R–134a refrigerants.

4.11.7 Where the use of plastic pipe is proposed in a secondary refrigerant system (e.g. brine), it is to be in accordance with Pt 5, Ch 12, 5 Plastic pipes.

4.11.8 Pipelines are to have ample provision for expansion and contraction in service conditions. In general, expansion bends are to be used for this purpose. However, the use of metallic expansion bellows will be accepted provided test data is produced showing satisfactory strength and fatigue properties under the appropriate conditions.

4.11.9 All pipelines are to be fully supported and secured so as to prevent vibration. Flexible hoses may be used, where necessary, to prevent transmission of vibration provided the documentation in Pt 6, Ch 3, 4.11 Piping systems 4.11.8 is provided. Flexible hoses are to be of a type which has been approved by LR, see Pt 5, Ch 12, 7 Flexible hoses.

4.11.10 Pipework, which may contain low temperature refrigerant, except within secondary refrigerant cooler rooms, is to be thermally insulated to an extent which will minimise condensation of moisture. Insulation in pre-formed sections is recommended. If in situ foamed insulation is employed, pre-production testing on site is to be carried out to the satisfaction of the Surveyor, using a `mock-up' representative of the system to be employed.

4.11.11 All pipe insulation is to be provided with an efficient vapour barrier, care being taken to ensure that it is not interrupted in way of supports, valves, etc. Also adequate protection of insulation surfaces from mechanical damage is to be provided.

4.11.12 Where refrigerating piping is embedded in the cargo chamber insulation, the locations of the pipe joints are to be marked on the outside of the insulation lining.

4.12.1 Butt welded pipe joints are to be employed as far as practicable. Socket welded pipe joints are acceptable up to 25 mm diameter. Flanged or other joints are to be kept to a minimum and, in general, are to be restricted to connections with items of machinery or components which may have to be removed for maintenance purposes. Connections to valves are normally to be welded unless they are of a type, or in a position, which precludes in situ maintenance.

4.12.2 Pipe connections to fittings (e.g. gauge lines, level controls) which are likely to be subjected to heavy corrosion, are to be of heavy gauge construction, or be made from suitable corrosion resistant materials.

4.13.1 Where liquid level indicators of the `see-through' variety are used they are to be of the flat plate type incorporating glass (or equivalent material) of heat resistant grade.

4.13.2 All level indicators are to be provided with automatic shut-off devices and isolating valves. Plate-type sight glasses which form an integral part of the component in which they are mounted (e.g. compressor crankcases, pressure vessels) are exempt from this requirement.

4.13.3 All level indicators are to be suitable for the system maximum working pressure and tested accordingly.

4.14.1 Refrigerating systems with automatic expansion valves are also to be provided with efficient hand expansion valves and the arrangement is to be such that the automatic expansion valves can be by-passed and isolated.

4.14.2 As an alternative, duplicate automatic expansion valves may be fitted, each valve to be capable of the required duty and operable with the other out of action.

4.15.1 Refrigeration systems are to be provided with relief devices, but it is important to avoid circumstances which would bring about an inadvertent discharge of refrigerant to the atmosphere. The system is to be so designed that pressure due to fire conditions will be safely relieved.

4.15.2 Pressure relief devices are to be mounted in such a way that it is not possible to isolate them from the part of the system which they are protecting except that, where duplicated, a changeover valve may be fitted which will allow either device to be isolated for maintenance purposes without it being possible to shut off the other device at the same time.

4.15.3 Relief discharge is to be led to a safe place above deck away from personnel accesses and air intakes. Discharge piping should be designed to preclude ingress of water, dirt or debris which may cause the equipment to malfunction.

4.15.4 For ammonia systems, discharge from relief valves is to be led through water before venting to the atmosphere. Vapour detectors are to be provided in the discharge pipes to activate audible and visual alarms in the event of a leakage of ammonia.

4.15.5 A pressure relief valve and/or bursting disc is to be fitted between each positive displacement compressor and its gas delivery stop valve, the discharge being led to the suction side of the compressor. The flow capacity of the valve or disc is to exceed the full load compressor capacity on the particular refrigerant at the maximum potential suction pressure. For these internal relief valves, servo-operated valves will be accepted. Where the motive power for the compressor does not exceed 10 kW, the pressure relief valve and/or bursting disc may be omitted.

4.15.6 Compressors protected by bursting discs are to be provided with automatic shutdown in the event of high discharge temperatures.

4.15.7 Each compressor is to be provided with automatic shutdown in the event of high discharge pressure. For refrigeration systems where the maximum working pressure is less than or equal to 4 MPa the automatic shutdown is to operate at a pressure in excess of normal operating pressure but no greater than 0,9 of the maximum working pressure. For refrigeration systems where the maximum working pressure is greater than 4 MPa the automatic shutdown is to operate at a pressure in excess of normal operating pressure but no greater than 0,95 of the maximum working pressure.

4.15.8 Each pressure vessel which may contain liquid refrigerant and which is capable of being isolated by means of stop or automatic control or check valves is to be protected by two pressure relief valves or two bursting discs, or one of each, controlled by a changeover device.

4.15.9 Pressure vessels which are interconnected by pipework without valves, so that they cannot be isolated from each other, may be regarded as a single pressure vessel for this purpose, provided that the interconnecting pipework does not prevent effective venting of any vessel.

4.15.10 Omission of one of the specified relief devices and the changeover device, as required by Pt 6, Ch 3, 4.15 Overpressure protection devices 4.15.8, will be allowed where:

• vessels are of less than 300 litres internal gross volume; or
• vessels discharge into the low pressure side by means of a relief valve; or
• vessels operating using only cargo gas and, which can be independently isolated and gas freed during normal cargo operations provided that a shelf spare is carried.

4.15.11 Sections of systems and components which could become full of liquid between closed valves are to be provided with pressure relief devices relieving to a suitable point in the refrigerant circuit.

4.15.12 Refrigerant pumps are to be provided with pressure relief valves on the discharge side, which may relieve to the suction side, or to another suitable location.

4.15.13 Suitable spring-loaded safety valves are to be provided on the cooling liquid side of condensers and the brine side of evaporators where the pressure from any pump or expansion of the liquid in the circuit could exceed the design pressure of the system or any component forming part of the cooling system.

4.15.14 Relief valves are to be adjusted and bursting discs so selected that they relieve at a pressure not greater than the design pressure of the system, as defined in Pt 6, Ch 3, 2.5 Design pressures.

4.15.15 When satisfactorily adjusted, relief valves are to be protected against tampering or interference by a wire with a lead seal or similar arrangement.

4.15.16 Valves which are arranged to discharge to the low pressure side of the system are to be substantially independent of back pressure and are to be of a type which has been approved by LR.

4.15.17 The minimum required discharge capacity related to air of the pressure relief device for each pressure vessel is to be determined as follows:

4.15.18 The rated discharge capacity of the pressure relief valves expressed in kg/s of air is to be determined in accordance with an appropriate recognised National Standard such as ISO 5149 Mechanical Refrigeration Systems used for Cooling and Heating – Safety Requirements.

4.15.19 The rated discharge capacity of a bursting disc discharging to atmosphere under critical flow conditions is to be determined by the following formula:

d

=

85, 75 mm

4.15.20 The bore of the discharge pipe shall be at least the same bore as the relieving device outlet. The size of a common discharge line serving two or more pressure relieving devices which may discharge simultaneously shall be based on the sum of their outlet areas. Where discharge lines are long or where the outlets of two or more pressure relieving devices are connected into a common line, the discharge piping shall be sized such that the back pressure at full relief rate does not exceed 10 per cent of the relief valve set pressure.

4.15.21 Due account is to be taken of the reaction force on a relief valve or on discharge piping during discharge and adequate support provided.

4.15.22 As carbon dioxide can form a solid powder at atmospheric pressure, there is a possibility that relief devices will choke if vented directly to atmosphere. The method used to guard against the formation of powder is to be submitted for consideration.

4.15.23 In carbon dioxide systems, overpressure protection is to be fitted to pipelines or components which can be isolated in a liquid full condition. Pressure relief devices are to be arranged such as to vent vapour at all times.

4.15.24 In cascade systems where carbon dioxide is used in combination with ammonia, the effects of carbon dioxide leaking into the ammonia side are to be considered. It may be desirable to design the ammonia system to either withstand the design pressure on the carbon dioxide side or have relief arrangements to safely deal with the additional vapour produced if a leak occurs.

4.16.1 Suitable filters are to be provided in the refrigerant gas lines to compressors and in the liquid lines to refrigerant flow controls. Wire gauze used in filters is to be sufficiently robust and well-supported. A filter may be combined with the oil separator required by Pt 6, Ch 3, 4.7 Oil separators 4.7.1. Stop valves are to be provided to allow for servicing of filters. After first commissioning of the system, the filters should be examined to confirm that elements remain intact and not collapsed.

4.16.2 Refrigerant filters, driers and moisture indicators are to be fitted in halocarbon refrigerant systems, and the arrangement is to be such that filters and driers can be by-passed, isolated and opened up without interrupting plant operations.

4.17.1 Where the operating pressure of the low pressure system may be below atmospheric, a purging device is to be provided, the discharge from which is to be led to a safe place above deck.

4.18.1 All sounding pipes, whether for compartments or tanks, which pass through refrigerated spaces or the insulation thereof, in which the temperatures contemplated are 0°C or below, are to be not less than 65 mm bore. The pipework is to be in accordance with the requirements of Pt 5, Ch 12 Piping Design Requirements and Pt 5, Ch 13, 2.9 Miscellaneous requirements.

4.18.2 Sounding pipes to oil compartments are not to terminate within refrigerated spaces or in their air cooler spaces, or are these pipes to terminate in enclosed spaces from which access is provided to refrigerated spaces or their air cooler spaces.

4.18.3 All pipes, including scupper pipes, air pipes and sounding pipes that pass through refrigerated spaces are to be insulated.

4.18.4 Where the pipes referred to in Pt 6, Ch 3, 4.18 Piping in way of refrigerated spaces 4.18.3 pass through chambers intended for temperatures of 0°C or below, they are also to be insulated from the steel structure, except in positions where the temperature of the structure is mainly controlled by the external temperature and will normally be above freezing point. Pipes passing through a deck plate within the ship side insulation, where the deck is fully insulated below and has an insulation ribband on top, are to be attached to the deck plating. In the case of pipes adjacent to the shell plating, metallic contact between the pipes and the shell plating or frames is to be avoided so far as practicable.

4.18.5 The air refreshing pipes to and from refrigerated spaces need not, however, be insulated from the steelwork.

4.19.1 Provision is to be made for the continuous drainage of the inside of all refrigerated spaces and cooler trays. The pipework is to be in accordance with the requirements of Pt 5, Ch 12 Piping Design Requirements and Pt 5, Ch 13, 3.2 Cargo holds.

4.19.2 All drain pipes from the refrigerated spaces and cooler trays are to be fitted with liquid sealed traps, which are to be of adequate depth and readily accessible for cleaning and refilling with brine. The pipes from lower spaces situated on the tank tops are also to be fitted with bilge non-return valves.

4.19.3 Where drains from separate refrigerated spaces join a common main, the branch pipes are each to be provided with a liquid sealed trap.

4.19.4 Sluices, scuppers or drain pipes which would permit drainage from compartments outside the refrigerated spaces into the bilges of the latter are not to be fitted.

4.19.5 Screwed plugs or other means for blanking off scuppers, draining chambers and cooler trays are not to be fitted. If, however, it is specially desired to provide means for temporarily closing these scuppers, they may be fitted with shut-off valves.

4.20.1 All steel bolts, nuts, hangers, brackets and fixtures which support or secure cooling appliances, piping insulation, meat rails, linings and prefabricated insulated panels, etc. are to be suitably protected against corrosion.

4.21.1 Components intended for use with a primary refrigerant are to be subject to strength and leak pressure tests as detailed in Table 3.4.2 Test pressure.

4.21.2 Component strength pressure tests are to be hydraulic or where suitable safety measures are taken, may be pneumatic. The latter is to be carried out with a suitable dry inert gas.

4.21.3 Component leakage pressure tests are to be carried out only after completion of satisfactory strength pressure tests. Pneumatic pressure is to be applied using a suitable dry inert gas.

4.21.4 Components for use with a secondary refrigerant or cooling water are to be hydraulically tested to 1,5 times the design pressure, but in no case less than 0,35 MPa g.

4.22.1 For primary refrigerant piping welded in place, strength pressure tests of the welds are to be carried out at a test pressure of 1,5p. This will normally take the form of a pneumatic test since hydraulic testing media such as water are not acceptable due to their incompatibility with the primary refrigerants and the difficulty of removing all traces from a completed system.

4.22.2 Pneumatic pressure tests are to be carried out using a suitable inert gas. All pneumatic tests are potentially dangerous and due precautions are to be observed.

4.22.3 Where pneumatic tests are prohibited by relevant authorities, the tests required by Pt 6, Ch 3, 4.22 Pressure test after installation on board ship 4.22.2 may be omitted provided non-destructive tests by ultrasonic or radiographic methods are carried out with satisfactory results on the entire circumference of all butt welds not tested in accordance with Pt 6, Ch 3, 4.11 Piping systems 4.11.3. Where ultrasonic tests have been carried out, the manufacturer is to provide the Surveyor with a signed statement confirming that ultrasonic examination has been carried out by an approved operator and that there were no indications of defects which could be expected to have a prejudicial effect on the service performance of the piping.

4.22.4 After completion of the test required by Pt 6, Ch 3, 4.22 Pressure test after installation on board ship 4.22.1, Pt 6, Ch 3, 4.22 Pressure test after installation on board ship 4.22.2 or Pt 6, Ch 3, 4.22 Pressure test after installation on board ship 4.22.3, a leak pressure test is to be carried out using a suitable inert gas at a pressure equal to the design pressure, in the presence of the Surveyor.

4.22.5 Secondary refrigerant piping welded in place is to be hydraulically tested to 1,5 times the design pressure, but in no case less than 0,35 MPa g.